Circuit arrangement for commutating a reluctance motor

Abstract

A circuit arrangement for commutating a reluctance motor including a current generator which produces first and second cyclic sequences of current pulses. In response to the first cyclic sequence applied to the stator windings of the motor, a rotor travels a predetermined distance along a motion coordinate path. Application of the second sequence to the stator windings results in the rotor traveling at least twice the predetermined distance along the motion coordinate path. The second sequence, which is applied when rotor speed exceeds a predetermined level, is formed by omitting predetermined current pulses from the first cyclic sequence.

We claim: 
     
       1. A circuit arrangement for commutating a reluctance motor having a stator and a rotor, the rotor traveling along a motion coordinate path relative to the stator, comprising: a plurality of stator windings; and   current generating means for producing a first cyclic sequence of current pulses resulting in the rotor traveling a predetermined distance along the motion coordinate path and for producing a second cyclic sequence of current pulses resulting in the rotor traveling at least approximately twice the predetermined distance along the motion coordinate path, said stator windings being supplied with said second cyclic sequence of current pulses when rotor speed exceeds a predetermined level;   wherein said second cyclic sequence of current pulses is formed by omitting predetermined current pulses from said first cyclic sequence.   
     
     
       2. The circuit arrangement of claim 1, wherein said first cyclic sequence includes the repetitive pattern of a first train of current pulses followed by a second train of current pulses followed by a third train of current pulses, said second cyclic sequence including the repetitive pattern of the first train of current pulses followed by the third train of current pulses followed by the second train of current pulses and wherein each train of current pulses is of predetermined length and phase relative to the motion coordinate path. 
     
     
       3. The circuit arrangement of claim 1, wherein each train of current pulses within the first cyclic sequence is of shorter duration than each train of current pulses within the second cyclic sequence. 
     
     
       4. The circuit arrangement of claim 2, wherein relative to the motion coordinate each train of current pulses within the second cyclic sequence ends at substantially the same position as a train of current pulses within the first cyclic sequence. 
     
     
       5. The circuit arrangement of claim 1, wherein the current generating means includes an asymmetrical H circuit associated with each stator winding having a first longitudinal branch common to all H circuits and a second longitudinal branch, said first longitudinal branch and each second longitudinal branch including switching means serially connected to rectifier means. 
     
     
       6. The circuit arrangement of claim 5 in combination with a DC voltage source has a positive terminal and a negative terminal, wherein the rectifier means of each second longitudinal branch having a cathode connected to the positive terminal of the DC voltage source. 
     
     
       7. The circuit arrangement of claim 6, wherein the switching means of the first longitudinal branch and the rectifier means of each second longitudinal branch are connected to the same terminal of the DC voltage source and wherein each asymmetrical H circuit also includes a transverse branch which includes the associated stator winding, each longitudinal branch having a junction joining together the switching means and rectifier means of that branch and one end of the associated transverse branch. 
     
     
       8. The circuit arrangement of claim 7, further including measuring means connected between one of the terminals of the DC voltage source and each of the second longitudinal branches. 
     
     
       9. The circuit arrangement of claim 1, further including signal generating means for generating a position signal representing the position of the rotor along the motion coordinate path. 
     
     
       10. The circuit arrangement of claim 9, further including processing means responsive to the position signal for producing a speed signal representing rotor speed. 
     
     
       11. The circuit arrangement of claim 10, wherein the rotor includes a plurality of poles and wherein said signal generating means includes a motion coordinate generating means connected to the motor and divided into a plurality of first segments and a plurality of second segments based on at least the plurality of rotor poles, said first segments and second segments forming an alternating contiguous pattern on said motion coordinate generating means. 
     
     
       12. The circuit arrangement of claim 11, wherein said signal generating means further include a plurality of sensing elements corresponding in number to the number of rotor poles and positioned about the motion coordinate generating means with adjacent sensing elements separated from each other by a fixed distance. 
     
     
       13. The circuit arrangement of claim 12, wherein said sensing means are operable for producing a first signal when sensing each first segment for a period of time corresponding to about twice the fixed distance along the motion coordinate path and for producing a second signal when sensing the second segment for a period of time corresponding to about four times the fixed distance along the motion coordinate path. 
     
     
       14. The circuit arrangement of claim 13, wherein each of the first segments is characterized by at least one of a first optical property, a first electrical property and a first magnetic property; said second segment being characterized by at least one of a second optical property, second electrical property and second magnetic property; each of said sensing means being operable for sensing the at least one property characterized by each of the first segments and the second segments. 
     
     
       15. The circuit arrangement of claim 10, wherein said processing means includes control means responsive to the position signal and a feedback signal representing the speed signal for producing control signals, said current generating means being responsive to said control signals for producing said first cyclic sequence of current pulses and said second cyclic sequence of current pulses. 
     
     
       16. The circuit arrangement of claim 15, wherein the switching states of each switching means of each second longitudinal branch is based on the control signals; the switching states of the switching means of each second longitudinal branch thereby reflecting the values of the position signal and speed signal.